| Compared with other materials, microalgae is a good source for biodiesel production due to their high lipid content, short growth cycle, high production capacity, easy to cultivation, rapid propagation and easy to extract the lipid and so on. But so far, microalgae is very difficult to be used in large-scale production of biodiesel because of lacking the algae which has big biomass, high lipid content and low cost of cultivation.Nitzschia closterium cells are rich in fatty acids, so it is a very important oleaginous microalgae. Some researches show that the nutrient condition and environmental factors can greatly affected the growth and synthesis of fatty acid in alga. In this study, Nitzschia closterium was mutagened by Ethyl Methanesulphonate (EMS), two different mutant strains were got, which both had stronger oil production capacity, higher protein,soluble sugar and chlorophyll content. And to explore biological effects of nutrient conditions and environmental factors on the mutant strain, the effect of N, P, Si, salinity, PH, temperature and light conditions on lipid content, protein content, soluble sugar content, chlorophyll content and growth of the mutant strain also were studied.The main results are as follows:1. In order to obtain the high-lipid producing strains of Nitzschia closterium, the method of chemical mutation with Ethyl Methanesulphonate (EMS) was used, and the biological effects of EMS on the cells of Nitzschia closterium also were studied. The results showed that the EMS has great effect on the cells of Nitzschia closterium, and two different mutant strains of Nitzschia closterium YA and YB were obtained after being treated by 0.1 mol/L and 0.05 mol/L dosage of EMS respectively, which both had stronger oil production capacity. Under the same cultivation condition and compared with the CK, the chlorophyll a, carotenoids, protein, soluble sugar contents and lipid relative content of YA and YB have increased by 30.05% and 25.77%,22.15% and 19.26%,9.06% and 8.27%,48.25% and 45.48%,44.06% and 12.86% respectively.2. The greatest nutrient assimilation efficiency, growth rate, chlorophyll content, soluble sugar content, protein content, and oil content were obtained at sodium nitrate as nitrogen source; there were significantly different compared to urea and ammonium chloride as nitrogen source.3. The N, P and Si single factor experiment showed that:The three kinds of nutrient elements have important influences on the cell density and oil production of YA. The fastest growth and highest chlorophyll, soluble sugar and protein content of YA was obtained when N, P and Si concentration is 17.6 10-4 mol·L-1,3.6 10-5 mol·L-1,2.2 10-4 mol·L-1 respectively. And when N, P and Si concentration is 2.2 10=4 mol·L-1,0.9 10-5 mol·L-1,0.27 10-4 mol·L-1 We got the highest lipid content in the cell of YA.4. The experiment about environmental factors showed that:The growth of YA reached the maximum at salinity 30%o, pH8,20℃,40001x, and the highest oil content were got at salinity 30 ‰, pH8,20℃,50001x. |
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